if it's the accord, you'll need an adapter to make it fit, but they are available. i don't know much about the current camry setup. actually, you usually need an adapter set even for normal stock DIN stereos, just because of varying mounting methods. and you'll want a wiring harness, of course. keep in mind you may or may not be able to use the steering wheel controls, depending on the stereo and adapters you buy.
that said, i can speak for the stock stereo in my 2003 Accord EX V6. it's the one of the better stock stereos i've heard, and i haven't felt the need to upgrade it, even though i'm a music freak. it's a big improvement over the previous generation's stereo, and way better sounding than the upgraded head-unit in my old accord.